Typical communication systems interconnect a variety of communication devices and offer a wide range of services. These services may include both call processing features such as on-hook and off-hook queuing and system management capabilities such as station message detail recording SMDR.
The queuing feature provides a calling party with efficient call processing. For example, when a trunk is not immediately available to a calling party following dialing, the calling party need not redial since the system will automatically queue the trunk request and complete the call connection when a trunk becomes available. SMDR is an administrative function which provides the customer with an accurate billing record of information for each call connection. Such information includes an identification of the calling and called stations, an indication as to the time of call placement and the duration of the call. Services of the type described are currently only available for those connections processed according to trunk call processing algorithms.
In the communication switching system, each analog facility is served by either a line port circuit or trunk port circuit. These ports include circuit boards having physical control points. The control points generate signals indicative of a present state i.e., on-hook or off-hook, of each associated analog device. A control processor in the switching system indirectly scans the ports and determines the state of the physical control points on the board in order to affect connect and disconnect call processing operations. The control processor responds to the generated signals and implements the appropriate call processing algorithms in response to port circuit type i.e., line or trunk.
Line call processing which serves line port circuit connections offer a user basic connect and disconnect services with only a limited number of system management capabilities. In contrast, trunk call processing which serves trunk port circuit connections offer the user an extensive number of services including those previously described. The control processor processes each connection according to the type of port and therefore, can only implement call processing features and system management capabilities when analog trunk ports are served.
In addition to serving analog facilities, the communication switching system also serves digital facilities such as terminals and host computers. Host computers typically serve a plurality of terminal users and require a large number of host computer access ports. Digital line port circuits are used to provide host computer access. Trunk port circuits are not used since trunk ports are more expensive, consume more physical space and severely limit the number of customers served by a single communication switching system arrangement. Therefore, all terminals and host computers are connected to the switching system via digital line ports, and connections between these digital facilities are processed according to line call processing algorithms.
As previously discussed, line call processing offers the user a limited set of services. Therefore it would be advantageous to provide, in an economic and efficient manner, call processing features and system management capabilities such as those available for trunk call processing for the digital line port circuit connections which serve terminal/host computer interconnections.